1. Field of the Invention
The present invention pertains to a method of producing minimum weight thin wall profile members for building structures with strict qualifying requirements to reliable operation and minimum weight of the structure.
2. Background Information
Widespread types of structural units applied in building and in mechanical engineering are compressed thin wall structure members constituting thin wall profile members. They enable to meet strict operational requirements with respect to articles providing resolution of the “weight-strength” compromise, viz., stability and stiffness under compressive force providing minimization of weight. Minimization of the weight of thin wall structures encounters the issue of lack of a single dependence interconnecting multitude of parameters, in particular, critical stress, external load, material, dimensions and shape of cross-section of a thin wall profile member.
Known thin wall profile members (hereinafter, TPMs) are made with a shape and cross section dimensions constant along their length, for example, a TPM of a closed triangular or rectangular shape comprising main strip(s) and additional strip(s) with common reinforcing ribs [Reference 1]; [Reference 2, p. 33, FIG. 20]. The drawback of this known TPM is the narrow range of its applicability related to the restrictions brought about by its specific shape. Besides, the relations of dimensions of the cross section of this TPM are not optimal from the viewpoint of its weight minimization.
Other TPMs are made with a shape and cross-section dimensions constant along their length and comprise main strip(s) and additional strip(s) with common reinforcing rib(s) and free reinforcing ribs. As TPMs of such kind, the most common types of TPMs can be considered, for example, I-shaped, Z-shaped, C-shaped, T-shaped, L-shaped, etc, [Reference 3]; [Reference 4]; [Reference 2, p. 32, FIG. 18; p. 122, FIG. 111; p. 153, FIG. 142]. Embodiments of TPMs having these shapes and with known ratios of cross-section dimensions are not optimal either in terms of weight minimization.
Also TPMs are made with shapes and cross-section dimensions constant along their length and comprise main strip(s) and additional strip(s) with common reinforcing ribs and free reinforcing rib(s) such as, for example, a U-shaped TPM, [Reference 5]; [Reference 6]; [Reference 7]; [Reference 8]; [Reference 2, p. 110FIG. 101:, p. 111, FIG. 102].
During the production of these TPMs with the thus selected cross-section dimensions [References 1-8], the effect of “spacing” of cross section material was not accounted for accurately enough. As a result, at a higher moment of inertia, the respectively higher overall stability is achieved, while the local stability is thereby reduced. Due to this, it proves impossible to establish how close is the selected version of cross-section dimensions to the one with the minimum area, hence with the minimum TPM weight.